Plasma display devices of this type are generally addressed via the coordinate drive lines by firing or erasing signals respectively, a sustain signal being applied via the same coordinate lines to maintain a continuous display.
In one embodiment of the sustain signal, an alternating voltage is continuously applied to the coordinate lines so that each half-period of the sustain voltage at the discharge gaps previously fired the combined influence of the sustain voltage on the wall voltages built up at dielectric electrode layers, there is a new firing. Upon the new firing of the discharge gaps with accompanying light emissions the wall charges, at each of the discharge gaps, are again generated but in a polarity which is opposite to the preceding one, until the gas discharge at the discharge gap is again extinguished temporarily. The sustain voltage of opposite polarity in the subsequent half-period again fires for a short time the discharge gap with a simultaneous re-charging of the wall charge which in turn extinguishes again the gas discharge. This process is repeated until an extinguishing pulse for suppressing a subsequent ignition is applied.
Formerly known embodiments of gas discharge display devices do not show any decoupling components on the substrates themselves which include the laminar discharge chamber. Consequently, components and circuit elements for the decoupling have to be housed separately outside the substrates which generally necessitates a considerable structural and manufacturing expenditure. In order to avoid this it is the object of the invention to provide a gas discharge display device permitting an uncomplicated manufacture and which during operation ensures an efficient decoupling between sustain voltage supply lines and firing and extinguishing pulse lines, as well as between the inidividual discharge gaps.
According to the invention this problem is solved in that the respective discharge gaps are defined by individual electrodes which, on the one hand, are connected via zones of low electric conductivity in at least one of the substrates encompassing the discharge chamber, to the sustain voltage supply line, and which on the other hand are capacitively coupled via highly insulating zones in a first dielectric layer on the respective substrate, to the firing or extinguishing pulse supply lines.
It is thus advantageously achieved that the necessary decoupling measures are directly contained in the indicating arrangement and are presented simultaneously with the latter's manufacture, so that the above mentioned decoupling elements, components, and circuit elements as well as their fixing and connecting measures are no longer required.
If the sustain voltage is applied in the form of alternating or pulse voltages, respectively, it is advisable to cover the electrodes towards the discharge chamber by a second dielectric layer in order to permit the formation of wall charges.
When the display device in accordance with the invention is used with a sustain voltage in DC operation the second dielectric layer is no longer required, which permits a further simplification of manufacture.
In an advantageous improvement the sustain voltage supply lines are each provided at each second space between two electrode columns in that two electrode columns are provided to one respective sustain voltage supply line.
The arrangement in accordance with the invention can basically be realized in two embodiments. In the first case it is provided that on a non-conductive substrate parallel sustain voltage supply lines and thus alternatingly firing or extinguishing pulse supply lines are arranged, and that thereon the first dielectric layer is applied which shows alternatingly highly insulating zones substantially carrying the electrodes, and poorly insulating zones contacting the electrodes of two respective adjacent electrode columns. It can advantageously be provided that the firing or extinguishing pulse supply lines provided above or beneath the electrode columns on the first dielectric layer are each planar-wise extended directly above the individual electrodes in order to achieve in that manner a maximum planar zone as a counter-plate to the respective circular electrode for forming a respective coupling capacity.
In the second case, it can be provided in an advantageous improvement of the invention that the substrate itself is of low conductivity and that the sustain voltage supply lines are on one plane with the electrodes on the substrate, the sustain voltage supply lines being arranged in parallel on both substrates, and being provided in an interleaved manner from substrate to substrate, i.e. in alternating spaces between the electrode columns. Such an embodiment presents the advantage, when sustain voltages are used in the form of alternating voltages, that only a single dielectric layer has to be applied which is required for generating the wall charges. Here, too, it can be advantageously provided that the firing or extinguishing pulse supply lines above each electrode are planar-wise extended so that the firing of extinguishing pulses can be applied via maximum coupling capacities.
In an advantageous embodiment of the invention it is provided that the sustain voltage supply lines are on ground potential on one of the substrates, and that the electrodes of this substrate serve each as a counter-plate for one of the plates coupled to the firing and extinguishing pulse sources, said plates being provided on an element displaceably arranged to said substrate in a series which is substantially transverse to the displacement direction, thus forming with the respective opposite electrodes coupling capacities as a function of the position of the element. This permits greater flexibility in the use of the display device in accordance with the invention, as the capacitive coupling of the firing pulses or the extinguishing pulses, respectively, can take place in a corresponding dependence of the supply of measured values to be displayed, as required for instance in radar devices, control indicator boards, etc.
Via corresponding wiper devices provided in the substrate frame on the one hand and in the displaceable element on the other, in a manner known per se, supply voltages as well as firing and/or extinguishing pulses can be transmitted to the displaceable element which in turn, in an advantageous design, is equipped with registers, drivers, and latches in an integrated circuit manner, as they are required for addressing the gas discharge gaps. With measures of that type the number of supply lines to the displaceable element can thus be restricted to a minimum.
This system in accordance with the invention in turn can be realized in two embodiments, i.e. on the one hand that a linear displacement of the element can be performed, and on the other that in the case of a circular design of the substrates surrounding the laminar discharge chamber an angular displacement of the element towards the polar coordinate position is provided. The latter embodiment is advantageously suitable for use with small radar devices.
An advantageous driving means of the circular element consists in that a peripheral drive co-acting therewith is provided which advisably can consist of several friction-coupled driving wheels. The disk rim of the element turnable in its angular position can be of such a design that the necessary supplies to the plates thereon are transferred via corresponding wiper devices to conductive lands at the frame of the screen which lead to the measuring points or scanning points, respectively, for supplying the signals to be represented. Here, too, however, it is again possible to provide register drivers, latches, etc. in the form of control modules on the element itself. For that purpose, the rim of the circular element for receiving these modules can be designed accordingly so that the disk surface as such can remain free.
The circular substrate arrangement in cooperation with the element which is turnable in its angular position and carrying the plates is excellently suitable for the use as a radar device as the synchronization between scanning and angular position of the element can simply take place mechanically.
In an advantageous embodiment of the invention it can furthermore be provided that the circular substrate and the circular, turnable element encompass a cavity filled with dielectric oil of high dielectricity constant in that in a manner known per se a lateral closing of the cavity under oil-proof seal is provided.